All posts tagged Monster Kelvin Wave

And so it appears we are living in a time of Monster Kelvin Waves — powerful confluences of Pacific Ocean heat running just beneath the surface — bringing with them the potential for both record global temperature spikes and strong, climate-wracking El Nino events.

(Building heat in Pacific Equatorial Surface waters on April 9 of 2015 — a sign of a massive pulse of hotter than normal water running at about 100 meters depth. A heat pulse that may be setting in place conditions for a powerful El Nino later this year. Image source: Earth Nullschool. Data Source: Global Forecast System Model.)

This immense heat pulse was enough to shove the equatorial region inexorably toward El Nino status. By September, mid-ocean values were hot enough to have reached the critical threshold of 0.5 C above surface value average. Perhaps more importantly, the Winter/Spring 2014 Kelvin Wave also contributed to record positive PDO values for the Pacific by December of 2014. A surface heat departure that was unprecedented to modern climates. Block-busting ocean warmth that almost certainly spurred 2014 global atmospheric temperatures to new all-time record highs in the current age of human warming.

Monster Kelvin Wave Redux

Now, a second, and equally strong monster Kelvin Wave is again rippling across the Pacific Ocean subsurface zone. A powerful pulse of heat that will reinforce the current weak, mid-ocean El Nino, lend energy to ridiculously warm Pacific Ocean sea surface states, and pave the way for a long-duration equatorial heat spike.

(Monster Kelvin Wave Redux. A second powerful Kelvin Wave is surging across the Pacific Equatorial Subsurface zones, strengthing prospects for both a continued El Nino and for a record hot year in 2015. Image source: NOAA/CPC.)

As we can see in the NOAA CPC rendering above, the current Kelvin Wave is a massive and extraordinarily warm beast of a thing. It encompasses most of the thousands-miles broad Equatorial Pacific with its hottest zone peaking at 5-6 degrees Celsius above average temperatures — a region that stretches from near the Date Line all the way to just west of Central America. At +1.75 C for the entire below-surface equatorial region, the current Kelvin Wave is already approaching last year’s peak values. Values it may well exceed in the coming days.

Overall, the current Kelvin Wave seems to have more connection to the surface environment than last year’s powerful surge. A massive plug of Pacific Ocean heat readying to belch back into the atmosphere.

But perhaps more concerning is the fact that a strong El Nino is again starting to show up in some of the long range models. NOAA’s CFS ensemble shows El Nino continuing to steadily strengthen throughout 2015 reaching overall Nino 3.4 surface values above +2.1 C by October, November and December of this year:

The departures we see in this long range forecast are extraordinary — rivaling or possibly exceeding the intensity of the 1998 Super El Nino. An event of this kind would result in powerful ocean and atmospheric surface temperature spikes, catapulting us well beyond the climate range previously established by the 1998 event. Globally, we would be entering new, record hot territory, possibly approaching 1 C above 1880s values for the 2015-2016 period.

Troubling Situation With High Uncertainty

As such, we should consider this to be a troubling situation, in need of close, continued monitoring. To this point, it is worth noting that El Nino prediction during Spring is highly uncertain. Last year’s very strong Kelvin Wave also set off predictions for a moderate-to-strong El Nino event by summer-through-fall. Though El Nino did eventually emerge, it was weaker and later in coming than expected. Now, a new set of conditions is setting up similar, and perhaps, even more intense ocean and atmosphere heat potentials.

Though still uncertain, what we observe now are ocean conditions that raise potentials for both extreme El Nino and human-warming related weather. Powerful ocean heat pulses of the kind we observe now, when combined with an extraordinary human greenhouse gas heat forcing, also increases the likelihood of another record warm year. El Nino associated droughts and heatwaves — particularly for South America, India, Australia and Europe through Central Asia are at rising risk. In the event of mid-ocean El Nino, the risk increases that the 1200 year California drought will continue or even intensify. If the heat pulse shifts eastward, a switch to much heavier rainfall (potentially terribly heavy) could coincide with a breaking of the Ridiculously Resilient Ridge pattern that has warded moisture away from the US West Coast for nearly three years. Extra heat of this kind would also tend to enhance precipitation extremes — more rain when it does rain and far more intense drought in areas affected by heat and atmospheric ridging.

Given the patterns we have observed over the last year, we could expect worsening conditions for some regions (India, Australia, some sections of South America, Eastern Europe) and the potential for a shift from one extreme to the next for other regions (US West Coast). These potentials depend on the disposition and intensity of surface heat in the Pacific, which bears an even closer watch going forward.

And the current El Nino is certainly an odd bird. According to reports from NOAA and the National Weather Service, the center of highest sea surface temperatures for the El Nino this year is offset westward — coming closer to the date line than it typically does. This is a weird heat disposition for El Nino which is, at least, a mid ocean event and often pushes warming well across the Pacific to South American shores.

(Pacific sea surface temperature anomaly [SSTA]. Note the hot water pools off both Australia and North America. These zones are joined by a vast blanket of warmer than average waters arranged diagonally across the Pacific from SW to NE. This disposition includes the warm anomaly along the Equator which is hot enough to reach weak El Nino status. But the disposition of sea surface temperatures throughout the Pacific, with highest equatorial anomalies near the date line and warmer spikes near Australia and the North American West Coast is unusual. SSTA graphic provided by Earth Nullschool. Data Source: Global Forecast System Model and NCEP.)

It’s also late in coming, as typical El Ninos have tended to arrive in full form during late fall or early winter. A Christmas-time warming of waters off the West Coast of South America was a traditional call-sign for El Nino and one that resulted in its name — which is Spanish for “The Christ Child.” Late winter and early spring are more typical times for the formation of deeper warmer water that may trigger an El Nino later in the year but often do not herald a fully-developed event (see What is El Nino? for more related information).

For earlier this week strong westerly winds began to roar against the typical flow of the trades along the Equator. The west wind back-bursts (WWB) push warmer West Pacific waters eastward and downward, enhancing the sea surface temperature anomaly spikes that fuel El Nino.

As of early Wednesday, March 11, these west winds had formed a gale force wall stretching just past the date line from about 5 North Latitude to 10 South Latitude. A gale driven by parallel cyclones — a weaker system to the north (Bavi) and the newly gathering Pam, which may challenge south Pacific records as the strongest storm ever to form in that region. In the above graphic we see a related ten minute sustained WWB of a rather extraordinary 85 kilometers per hour (about 50 mph) along the 7.45 degree South Latitude line.

Strengthening Kelvin Wave in a Record Warm World

Just before the formation of these strong westerlies, sub-surface temperatures also began to spike. A warm Kelvin wave that had already started its run beneath the sea surface, as of March 4, was beginning to show signs of strengthening well in advance of the added shove coming from the vigorous WWB shown above.

Peak temperatures in the wave as of a week ago had hit more than +6 C above average. A heat signature that is starting to look, more and more, like the very powerful Kelvin Wave of early 2014 that belched so much warmth into the atmosphere and likely contributed to both the current strongly positive PDO as well as 2014’s new record high temperatures.

(Sea surface temperature signature of an El Nino Modoki, which is closer to what we are seeing now, even if the higher temperature levels are currently shifted more toward the Date Line. Image source: Japan Agency for Marine-Earth Science.)

During recent years, some scientific reports have indicated that Central Pacific Warming or El Nino Modoki will be more prevalent as a result of human-caused climate change. Study authors Tong Lee and Michael J McPhaden, in the 2010 paper entitled Increasing Intensity of El Nino in the Central Equatorial Pacific note that increases in Pacific Ocean temperatures are primarily expressed through more intense warming of the central regions:

Satellite observations suggest that the intensity of El Niño events in the central equatorial Pacific (CP) has almost doubled in the past three decades, with the strongest warming occurring in 2009–10. This is related to the increasing intensity as well as occurrence frequency of the so-called CP El Niño events since the 1990s. While sea surface temperature (SST) in the CP region during El Niño years has been increasing, those during neutral and La Niña years have not. Therefore, the well-documented warming trend of the warm pool in the CP region is primarily a result of more intense El Niño events rather than a general rise of background SST.

If so, it seems possible that global warming may well be influencing the rather strange El Nino evolution we are witnessing now.

In any case, Central Pacific Warming El Ninos have a somewhat different impact than Eastern Pacific Warming El Ninos. For one, they tend to ramp up, rather than cool down North Atlantic Hurricanes. They also tend to result in more, not less, drought for the US West Coast. For India, mid-ocean warming of the kind we are seeing now can result in an enhanced disruption of the Asian monsoon — kicking off drought and related food security risks.

Tong Lee and Michael J McPhaden continue by adding:

…. the amplitude of this new type of El Niño has increased in recent decades (Lee and McPhaden 2010). For convenience, hereinafter we refer this new type of El Niño as to CP warming (CPW). Compared with the canonical EPW, the CPW exhibits distinctly different impacts on worldwide climate. For example, the CPW shifts the anomalous convection westward and usually forms two anomalous Walker circulations in the tropical Pacific (Ashok et al. 2007; Weng et al. 2007; Weng et al. 2009). The westward displaced convection was suggested to be more effective in causing Indian drought (Kumar et al. 2006). The CPW increases hurricane frequency both in the Atlantic Ocean (Kim et al. 2009) and western North Pacific (Chen and Tam 2010), and also shifts tropical cyclone tracks in the western North Pacific (Hong et al. 2011).

(Very powerful Kelvin Wave still moving eastward even as it begins to sink in off the coast of South America. Image source: NOAA.)

Likelihood for a significant El Nino later this year continued to increase as the most powerful Kelvin Wave on record continued its progress into the Eastern Equatorial Pacific. According NOAA’s recent April 13 assessment, the massive slug of anomalously hot Pacific subsurface waters continued to surge eastward, to deepen the 20 C isotherm and to spread out on or just below the surface.

A significant downwelling oceanic Kelvin wave that was initiated in January greatly increased the oceanic heat content to the largest March value in the historical record back to 1979 and produced large positive subsurface temperature anomalies across the central and eastern Pacific.

Extraordinary temperature departures in the range of 4-6 C above average stretched from a zone from 180 West Longitude to 80 West Longitude and ranged in depth from 30 to 70 meters. This very large zone of above average heat shattered global records even as it slid into position to begin re-delivering that excess to the atmosphere.

Perhaps more importantly, the nose of this wave of far warmer than normal water had begun to sag, pushing the 20 C isotherm deeper into the Eastern Pacific even as cooler water from the depths began to punch into the tail of the record hot Kelvin Wave, raising the 20 C isotherm in the Western Pacific. This downwelling force of a monster Kelvin wave appears to just now be initiating the start to a global weather-altering El Nino.

Hot Water Downwelling, Weakening Trade Winds

In the East, from 12 February to 13 April, the 20 C isotherm had plunged from about 25 meters below to around 100 meters of depth. During the same period, the isotherm from about 150 East Longitude to 170 West had risen from about 210 meters to 170 meters. At the subsurface, a continued rising of the isotherm in the West and its continued fall in the East would complete the transfer of warm waters across the Pacific and open the flood gates to the start of what could be an extraordinarily strong El Nino event as what is now a record Pacific Ocean heat content starts bleeding back to the atmosphere.

(20 C isotherm continues to rise in the Western Pacific [left side of graph] even as it rises in the East [right side]. Image source: NOAA.)

On the surface, trade wind weakening and reversals continued with a significant, though milder than those seen in January and February, backflow emerging in early April east of the Solomon Islands and coinciding with rather weak trade winds across the Equatorial Pacific. Such conditions continued to provide surface impetus to transfer warm waters across the Pacific even as record subsurface heat continued its transition eastward.

Chances for El Nino Rise

Accordingly, predictive forecasts both by NOAA and Australia’s Bureau of Meteorology are showing increasing potentials that El Nino will emerge. NOAA’s forecast now indicates that the chance for El Nino has jumped to over 50% by this summer and to 66% by the end of the year. Australia’s forecast is now showing a greater than 70% chance of El Nino over the same period.

Many of these impacts, though expected in a normal El Nino year appear to be enhanced by effects related to human caused climate change such as sea ice loss and an amplification of the hydrological cycle increasing the frequency of extreme rainfall, drought and fire events (as in the California drought and the southeast Asian and Siberian fires).

(El Nino model runs by NOAA’s Climate Prediction Center show 66% potential for El Nino Development by November, December and January of 2014-2015. Image source: CPC/IRI.)

During a typical strong El Nino year, global weather disruptions can cause severe damage resulting in reductions to world GDP by as much as 5%. But with the added and enhanced severe weather effects due to climate change interacting with El Nino, overall impacts could be far more destructive. In addition, a release of what is currently record Pacific Ocean heat content into the atmosphere will likely set off new high temperature extremes, further pushing the global climate system toward the very dangerous 2 C warming threshold.